Scanner color reproduction ability test

Most scanners have been calibrated at the factory, but due to differences in manufacturing conditions, changes in the color temperature of the light source, newness, etc. will affect the scanner's pointer. When purchasing flatbed scanners, manufacturers typically provide a standard transmissive or reflective original that includes a neutral grey scale and partial color patches. After normal scanning of the standard manuscript, observe the image in a certain line in Photoshop6.0 (observe the white line or black line is particularly obvious) whether the RGB three-channel pixels coincide, in order to check the scanning accuracy (observe should choose at high magnification ). The RGB channels do not correspond to pixels. On the one hand, it affects the sharpness of the scanned image, and on the other hand, it affects the color reproduction effect during the copying process.

Neutral ash scales were used to examine the ability of the flatbed scanners to restore neutral gray color and to express changes in the density level of the ladder. The correct restoration of the neutral gray color by the scanner is the premise and basis for identifying colors and restoring colors. Scanning color deviation is caused by the difference in the color performance of the scanning components and the standard components during the scanning process. Even though the scanner has been calibrated before shipment, some color casts are inevitable in use. In the actual process, the display screen is often corrected so that it can correctly display the color, and then correct the scanning color cast.

At present, the prepress production center uses medium and high document scanners. Most of the software can customize the output profile. For example, the RGB output characteristics culture can be defined in the NewColor software of Heidelberg. Just set the output profile in the scanning software to be the same as the "RGB setting" in PhotoShop so that the picture in PhotoShop closely matches the screen display in NewColor. Scanner profiles are not supported for scanners with lower file sizes. You can use the features of PhotoShop.

When correcting the color cast in the scan, the scanned neutral gray scale is placed into the Photoshop6.0 image processing software. The information palette is used to display the RGB values ​​of the steps in the image, and the Curves curve is used to adjust the RGB three channels. Until the CMYK display values ​​of the steps in the image reach the required values ​​for neutral gray, a visual neutral gray scale can be visually observed on the display screen. The Curves curve at this time is the color curve after the scanner corrects the color cast. When the image is scanned, the color after scanning should be properly compensated according to the curve. The curve can be saved for calling. By scanning with the color patches in the standard document, the scanner can determine the reproduction characteristics of each color. The visual contrast between the original color patch and the scanned image can qualitatively recognize which colors the scanner reproduces better, and which colors are worse, so that in the future, in the scanned image, the color of poor reproducibility is corrected by the image processing software. In addition, the scanner should be calibrated regularly.